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An experiment in Australia suggests that the dietary concentration of non-phytate phosphorus may influence the calcium-specific appetite of broilers and that the birds attempt to balance their intakes of these two nutrients.

The effect of dietary non-phytate phosphorus (nPP) and calcium concentration on the calcium appetite in broilers was evaluated by Stuart Wilkinson of the University of Sydney in Australia and co-authors there and with AB Vista Feed Ingredients in the UK.

According to their paper in Poultry Science, a total of 288 one-day-old male Ross 308 broilers were fed a commercial diet for seven days and then randomly allocated to one of eight dietary treatments for a 28-days study.

Diets were corn-soybean meal based and formulated to be nutritionally adequate except for nPP and calcium. Two concentrations of calcium (5.0 and 10.0g per kg) and four of nPP (2.5, 3.5, 4.5 and 5.5g per kg) were used, and all birds had access to a separate calcium source (calcium carbonate).

Birds fed 5.0g of calcium per kg diets consumed more (P<0.01) of the separate calcium source than birds fed diets containing 10.0g of calcium per kg. Increased consumption (P<0.01) of the separate calcium source was associated with increasing nPP concentration.

Bird performance was not influenced by dietary treatment.

Birds fed 5.5g nPP per kg diets had lower (P<0.01) digestibility of dry matter, crude protein and energy than the other groups.

Phosphorus digestibility was reduced in birds fed high calcium diets and those fed 2.5g nPP per kg diets (P<0.001). Birds fed 2.5 g of nPP per kg had lower tibia ash values than those fed higher concentrations of nPP while feeding diets containing 10.0g of calcium per kg led to higher concentrations (P<0.05) of tibia ash than for birds fed 5.0g of calcium per kg.

This study confirms previous findings that birds are able to meet their calcium requirement when fed calcium separately from the mixed ration, concluded Wilkinson and co-authors. They highlight that consumption of the separate calcium source responded to not only calcium concentration but also to the amount of nPP in the diet.

These data suggest that dietary nPP concentration influences the calcium-specific appetite of broilers, and this may indicate that birds attempt to regulate their intake of calcium relative to nPP. The researchers added that this may be mediated via a physiological mechanism to maintain an appropriate intake ratio of calcium to nPP.